This invention is directed to an apparatus and process for high voltage conditioning cathode ray tubes and more specifically to effect high voltage conditioning of cathode ray tubes having a tendency to arc between the external base pins rather than between the internal electodes of the cathode ray tube.
In the field of cathode ray tube manufacturing and particularly the manufacture of cathode ray tubes suitable for television receivers, it is common practice to apply a high voltage potential to the electrodes during the manufacturing process in order to remove undesired contaminents and protuberances from the electrodes. As is well known, such high voltage conditioning or "spot knocking" tends to inhibit the occurrence of inter-electrode arcing during normal operation of the cathode ray tube. As a result, undesired and unsightly flashes on the viewing screen as well as deleterious and sometimes catastrophic effects on associated operating circuitry are eliminated or at least reduced by the high voltage conditioning process.
Previously and presently in many types of cathode ray tubes being manufactured, it was and still is a common practice to apply a high voltage potential to an anode electrode sealed into the funnel-like portion of the cathode ray tube. The remaining internal electrodes are connected in common to circuit ground or to a conditioning potential source affixed to the base pins of the cathode ray tube. Thus, arcing is effected at the gap intermediate the anode and the remaining electrodes internal to the cathode ray tube.
Although the above-mentioned technique has been and still is extensively employed, it has been found that such techniques are not satisfactory for some cathode ray tube structures. More specifically, cathode ray tube structures such as the so-called tri-potential focus type cathode ray tube utilize relatively high potentials during operation and these high potentials are applied to the internal electrodes by way of the external contacts or base pins. Since these electrodes are subjected to relatively high potentials during operational use, it is imperative that each electrode and the gaps intermediately adjacent thereto be subjected to high voltage conditioning during the manufacturing process in order to remove undesired particles and protuberances from the electrodes prior to the normal operating experience.
Unfortunately, it has been found that coupling all of the electrodes in common to a conditioning potential souce and an anode electrode to a high voltage potential source does not provide the desired internal conditioning of each of the electrodes. Rather the gap intermediate the anode and the commonly connected grid electrodes appears to be the only area whereat the desired conditioning is effected.
Moreover, when one attempts to apply a conditioning potential to individual grid electrodes by way of the base pins, it has been found that arcing tends to occur externally at the base pins rather than internally at the electrodes. In other words, the external contacts or base pins tend to arc at lower potentials than are required to effect arcing intermediate the electrodes internal of the cathode ray tube.